1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and more particularly, to a method for fabricating an LCD having a liquid crystal dropping method applied thereto.
2. Background of the Related Art
Keeping pace with development of an information oriented society, demands on displays increase gradually in a variety of forms, and, recently to meet the demands, different flat display panels, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), ELD (Electro Luminescent Display), VFD (Vacuum Fluorescent Display), and the like, have been under development, and some of which are employed as displays in various apparatuses.
The LCDs have been used most widely as mobile displays while the LCDs replaces the CRT (Cathode Ray Tube) owing to features and advantages of excellent picture quality, lightweight, thin, and low power consumption. Besides the mobile type LCDs, such as a monitor of a notebook computer, the LCDs are under development for televisions (TVs) for receiving and displaying broadcasting signals, and computer monitors.
Despite the various technical developments in the LCD for serving as a display in different fields, the studies for enhancing a picture quality of the LCD as a display are inconsistent as to the features and advantages of the LCD in many aspects. Therefore, for employing the LCD in various fields as a general display, the key for development of the LCD lies on whether the LCD can implement a high quality picture, such as a high definition, a high luminance, and a large sized screen while the LCD has a light weight, thin, and a low power consumption.
The LCD is provided with a liquid crystal display panel for displaying a picture, and a driving part for providing a driving signal to the liquid crystal display panel, wherein the liquid crystal display panel has first and second glass substrates bonded together with a gap between the substrates, and a liquid crystal layer injected between the first and second glass substrates.
On the first glass substrate (a TFT array substrate), there are a plurality of gate lines arranged in one direction at fixed intervals, a plurality of data lines arranged in a direction perpendicular to the gate lines at fixed intervals, a plurality of pixel electrodes in respective pixel regions defined at crossing points of the gate lines and the data lines to form a matrix, a plurality of thin film transistors switchable in response to a signal from the gate lines for transmission of a signal from the data line to the pixel electrodes.
The second glass substrate (a color filter substrate) has a black matrix layer for shielding light from parts excluding the pixel regions, a red, green, blue (R, G, B) color filter layer for displaying colors, and a common electrode for implementing a picture.
The foregoing first and second substrates are bonded together, spaced by spacers, with sealant having a liquid crystal injection opening therein, through which liquid crystal is injected.
The liquid crystal is injected by evacuating the space between the two bonded substrates and dipping the liquid crystal injection opening in liquid crystal. The liquid crystal flows in the space between the two substrates by the capillary tube phenomenon. Once the liquid crystal is injected, the liquid crystal injection opening is sealed by the seal.
However, the related art method for fabricating an LCD having the liquid crystal injection method applied thereto has the following problems.
First, the related art method has poor productivity because the dipping of the liquid crystal injection opening in a liquid crystal while the space between the two substrates are maintained at a vacuum for injection of the liquid crystal, takes a long time.
Second, the liquid crystal injection, particularly, into a large sized LCD, is liable to cause imperfect filling of the liquid crystal in the panel, which is a cause of a defective panel.
Third, the complicated and lengthy time of the fabrication process results in requiring many liquid crystal injection devices, that occupy a lot of space.
Accordingly, a method for fabricating an LCD by using a liquid crystal dropping method has been researched. A Japanese laid-open patent publication No. 2000-147528 discloses the following liquid crystal dropping method.
A related art method for fabricating an LCD having the foregoing liquid crystal dropping method applied thereto will be explained. FIGS. 1A-1F illustrate the steps of a related art method for fabricating an LCD.
Referring to FIG. 1A, ultraviolet (UV) sealant 1 is coated on a first glass substrate 3 having a thin film transistor array formed thereon to a thickness of approx. 30 xcexcm, and liquid crystal 2 is dropped on an inner side of the seals 1 (a thin film transistor array part). No liquid crystal injection opening is provided in the seal 3.
The first glass substrate 3 is mounted on a table 4 in a vacuum container xe2x80x98Cxe2x80x99 which is movable in a horizontal direction, and held by a first suction device 5 holding an entire bottom surface of the first glass substrate 3 by vacuum.
Referring to FIG. 1B, an entire bottom surface of the second glass substrate 6 having the color filter array formed thereon is held by a second suction device 7 by vacuum, and the vacuum container xe2x80x98Cxe2x80x99 is closed and evacuated. The second suction device 7 is moved downward in a vertical direction until a gap between the first and second glass substrates 3 and 6 becomes 1 mm, and the table 4 with the first glass substrate 3 thereon is moved in a horizontal direction, to pre-align the first and second glass substrates 3 and 6.
Referring to FIG. 1C, the second suction device 7 is moved downward until the second glass substrate 6 comes into contact with the liquid crystal 2 or the seal 1.
Referring to FIG. 1D, the table 4 with the first glass substrate 3 thereon is moved in a horizontal direction to align the first and second glass substrates 3 and 6.
Referring to FIG. 1E, the second suction device 7 is moved downward until the second glass substrate 6 comes into contact with the seals 1, and is pressed downward until a gap between the second glass substrate 6 and the first glass substrate 3 becomes 5 xcexcm.
Referring to FIG. 1F, the bonded first and second glass substrates 3 and 6 are taken out of the vacuum container xe2x80x98Cxe2x80x99, a UV beam is directed towards the seal 1, to set the seal 1, thereby finishing fabrication of the LCD. In the seal 1, there are main seals and dummy seals surrounding an active region of the LCD.
However, the foregoing related art method for fabricating an LCD having the liquid crystal dropping method applied thereto has the following problems.
First, the sealant coating and liquid crystal dropping on the same substrate requires a long fabrication time period before the two substrates are bonded.
Second, as the sealant is coated and the liquid crystal is dropped on the first substrate while no progress is made for the second substrate, there is an unbalance of a fabrication process between the first and second substrates, which implies an ineffective operation of the production line.
Third, because the sealant is coated and the liquid crystal is dropped on the first substrate, the first substrate with a coat of the sealant applied thereto cannot be cleaned by an ultra sonic cleaner (USC). Therefore, as the sealant that is to bond the two substrates should not be washed away, particles cannot be removed, which may cause defective contact of the sealant during bonding.
Fourth, the movement of bonded substrates yet to be set for venting, or for unloading after the venting, is liable to cause misalignment as a size of the substrate increases.
Fifth, it is difficult to maintain a bonded state in subsequent steps until the sealant is set as the size of the substrate increases.
Sixth, the movement of the liquid crystal between the substrates caused by the misalignment of the substrates causes defective orientation of the liquid crystal.
Seventh, the misalignment of the substrates deteriorates the aperture ratio.
Eighth, the defective orientation of the liquid crystal is liable to cause blots like scratches, and blots related to a luminance.
Ninth, the bonding of the two substrates only by a physical force of the table and the second suction device may cause defective bonding due to non-uniform application of pressure throughout the substrate in a case where levels of the table and the second suction device are not correct.
Tenth, the introduction of air into the vacuum container for restoring the vacuum container into atmospheric pressure after the bonding may deteriorate a state of the vacuum container due to moisture contained in the air.
Accordingly, the present invention is directed to a method for fabricating a liquid crystal display (LCD) that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An advantage of the present invention is to provide a method for fabricating an LCD having the liquid crystal dropping method applied thereto, which can shorten a fabrication time period, and apply a pressure uniformly to prevent misalignment of the substrates.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the method for fabricating a liquid crystal display (LCD) includes providing a first substrate, and a second substrate having seals formed thereon; loading the first and second substrates into a bonding chamber; bonding the first and second substrates; setting the bonded first and second substrates; venting the bonding chamber for applying a pressure to the first and second substrates; and unloading the first and second substrates having the pressure applied thereto.
Loading includes providing upper and lower stages holding the first and second substrates by vacuum in the bonding chamber respectively; pre-aligning the first and second substrates; positioning a glass receiver of a bonding machine under the second substrate held at the upper stage; and providing respective stages holding the first and second substrates by electro static charge (ESC).
Bonding includes varying the pressure at least in two stages.
Setting bonded first and second substrates includes directing a light, or applying heat to the sealant of photo or thermosetting material, for setting the bonded substrates.
The sealant includes main seals and setting seals, and setting the bonded first and second substrates includes setting the setting seals for setting the two substrates.
The sealant includes main seals for sealing the liquid crystal dropped on the plurality of panels; a dummy seal for protecting the plurality of main seals; and setting seals for setting the bonded two substrates. Setting the bonded first and second substrates includes setting the setting seals for setting the first and second substrates.
The setting seals are formed on a periphery of the substrate, or between the panels.
The sealant includes main seals for sealing the liquid crystal dropped on the plurality of panels, and a plurality of dummy seals for protecting the plurality of main seals respectively, and setting the bonded first and second substrates includes setting the dummy seals for setting the first and second substrates.
Venting the bonding chamber for applying a pressure to the first and second substrates includes finishing moving the upper stage upward from the bonding machine, and injecting gas or dry air into the bonding chamber.
Venting the bonding chamber for applying a pressure to the first and second substrates includes injecting gas or dry air into the bonding chamber after moving the upper stage upward from the bonding machine and before finishing the moving the upper stage upward.
Venting the bonding chamber for applying a pressure to the first and second substrates includes injecting gas or dry air into the bonding chamber at the simultaneously with moving the upper stage upward.
Gas or dry air is blown through vacuum suction holes in the upper stage while the upper stage of the bonding chamber is moved upward.
Venting the bonding chamber for applying a pressure to the first and second substrates includes starting injection of gas or dry air into the bonding chamber, and moving the upper stage upward from the bonding machine.
Moving the upper stage upward from the bonding machine is carried out while gas or dry air is blown through vacuum suction holes in the upper stage of the bonding machine.
Venting the bonding chamber for applying a pressure to the first and second substrates includes injecting the gas or the dry air into the bonding chamber in two stages.
Venting the bonding chamber includes applying a pressure until a gap between the two bonded substrates is below 5 xcexcm.
Liquid crystal is dropped on the first substrate.
Unloading includes loading at least one of the first and second substrates to be bonded next on the upper or the lower stages, and unloading the set substrates.
In another aspect of the present invention, there is provided a method for fabricating an LCD including loading first and second substrates having liquid crystal dropped thereon and seals formed thereon into a bonding chamber; bonding the first and second substrates; venting the bonding chamber for applying a pressure to the first and second substrates; and unloading the first and second substrates.
The method for fabricating an LCD further includes aligning the first and second substrates before bonding the first and second substrates.
In further aspect of the present invention, there is provided a method for fabricating an LCD including loading a first substrate and a second substrate having sealant coated thereon into a bonding chamber; bonding the first and second substrates; venting the bonding chamber for applying a pressure to the first and second substrates; and unloading the set first and second substrates.
The sealant includes main seals and setting seals, and setting the pressed first and second substrates includes setting the setting seals for setting the first and second substrates.
A plurality of the setting seals are formed on a periphery of the substrate.
The sealant includes main seals for sealing the liquid crystal dropped on the plurality of panels, a dummy seal for protecting the plurality of main seals, and setting seals for setting the bonded two substrates. Setting the pressed first and second substrates includes setting the setting seals for setting the first and second substrates.
A plurality of the dummy seals are formed on an outer periphery of the plurality of main seals, respectively.
The sealant includes main seals for sealing the liquid crystal dropped on the plurality of panels, and a plurality of dummy seals for protecting the plurality of main seals respectively, and setting the pressed first and second substrates includes setting the dummy seals for setting the first and second substrates.
The dummy seals are set partly.
Setting the pressed first and second substrates includes coating adhesive having an excellent setting capability superior to the sealant on a cutting part or a periphery of the second substrate in forming the seals, and setting the pressed substrates by the adhesive.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.